The invention relates to a floor heating device comprising an electric heating cable extending in lengths forwards and backwards underneath the floor surface to be heated.
Various prior-art devices exist for heating and heat-regulating a floor surface with the aid of an electric heating cable. For example from EP,B1,588 911 is already known a floor structure according to which flooring panels are deposited on a floor surface in spaced-apart relationship so as to form inter-panel channels in which the heating cable is received. The structure also comprises a heat-reflecting sheet applied on the metal panels and tucked into the channels underneath the heating cable.
This arrangement results in a comparatively complex structure and considerable work is required to produce a heatable floor. It is, for example, necessary to deposit the panels and fix them in a predetermined spaced-apart relationship to ensure that the width of the formed channels is adapted to the width of the heating cable that is to be placed inside the channels. The application of the heat-reflecting sheet involves even more extra work.
From EP,B1,360 889 is further known a heating element in the form of a panel formed with channels disposed in parallel and housing a heating cable extending inside the channels. The device comprises semispherical bodies located between the channel mouths, on two opposite sides of the panel, and these bodies form rounded surfaces against which the cable abuts when formed into bends as it exits from one channel to enter into the adjacent one, for the purpose of preventing buckling or cracking damages on the cable. However, this construction is not intended to be built into floors and to serve as a floor heating means but if forms in itself a complete independent heating panel.
The invention provides a floor heating device, which is a further development of the prior-art technology and which permits installation in a rapid, practical and convenient manner of a heating cable in a floor, irrespective of the foundation or structure of the latter.
The floor heating device in accordance with the invention utilizes a so called self-regulating cable, a feature which further facilitates the installation of floor heating, irrespective of the type of flooring concerned, as will appear from the following description.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitative of the present invention, and wherein:
A self-regulating cable comprises two conductors arranged in parallel and surrounded by a semi-conductive plastics material, the conductivity of which varies with the temperature and ceases completely at sufficiently elevated temperatures. When the two conductors are connected to different electrical potentials, a current flows radially through the semi-conductive plastics material intermediate the conductors along the entire cable, whereby heat is generated. The magnitude of the current varies with the conductivity of the plastics material and is at is peak at the lowest-temperature regions of the cable, in which regions consequently heat is generated, and at its bottom at the highest-temperature regions of the cable, in which regions consequently less heat is generated. In this manner, the heating capacity of the cable becomes self-regulating. In addition, the fire-resistance of the cable is higher than that of a conventional cable, since the current between the conductors, and in consequence thereof the heating efficiency, ceases completely in the sections of the cable where the temperature is too high. In addition, a self-regulating cable may be severed into arbitrary lengths, since each conductor need only be connected to its respective potential at one of its ends.
The fact that the electric heating cable is self-regulating is a condition for easy installation in all situations of the device in accordance with the invention. A conventional electric cable, were it arranged in the inventive panels, would fail to satisfy the fire-safety regulations when used for example in combination with wooden flooring applied directly on top of the panels.